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2007/05/28
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LM3916 based sound sensor

by Sébastien Lelong — posted at 2007-05-28 13:52 last modified 2008-04-19 11:15
Last time, I've made a few test about a simple sound sensor (which I couldn't make work, but I'm not giving up...). This time, it's a bit more complex, since this sensor has a LM3916 dot/bar display driver:
  • at the beginning, there's the same preamp electret mic LM386-based,
  • output is connected to the LM3916 (constructor's schematics)



The idea is the following : this sound sensor will be used within the TweetyBot project, to detect when the birds sing loud (means "like a pig") or soft (means "tweetering in the fresh air of the morning"). If they sing loud, the display driver will trigger high db LEDs. Using and/or gates (Master Fenyo said), I could connect the 10 LM3916 outputs to 4 input pins (2^3 < 10 < 2^4). It's like an ADC, but levels are "steppized" (hum, I mean not continue...). Anyway, even without those considerations, the result is quite nice...
 




Just for the fun, this is one of my pretty birds, singing (almost) like a pig...

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SirBot Project

Re:LM3916 based sound sensor

Posted by Jeff at 2007-05-28 13:52
Hi i have never made a circuit board in my life, but im wanting to make one similar to yours for the tweetybot project. what im trying to do is make one that has about 20 led lights on a board that is 11 inches long. i want it to light up to sound.. low db low led lights light up.. and high db all the led light up.. hope you can understand what im trying to say.. well i was wondering where i should start looking to make this board or if you could help me on how to. thanks

Re:LM3916 based sound sensor

Posted by admin at 2009-04-30 08:06
Hi,
Part of this board comes from a sound sensor IIRC, you can look at my SirBot project, specifically: http://sirbot.org/sirbot-modules/sound-sensor/ (also look at parent level, there are many other boards). This other part is based on LM3916. Look at the datasheet, diagrams are provided, I took one of them. IIRC LM3916 can plugged in serial so they can handle lots of LED. If not LM3916, search for other chips of this type (LM39xx ?, bar LED).

Best o' luck !

Seb

Sound Sensor Question

Posted by Sebastian at 2009-07-03 16:22
Hello.
I'm trying to use your sound sensor for a school project.
I need to know what is the voltage range that the sensor can provide.
What is the maximum decibel level it can use and what voltage will it indicate in that case?
Does it have something like 0dB - 0V .. 80dB - 5V?

I'm asking because I want to connect it to the ADC of an atmel mega16 and i need to know what voltage reference I need set on the microcontroller so that the conversion is done correctly.

Thanks

Re:LM3916 based sound sensor

Posted by sirloon at 2009-07-03 19:49
Output voltage IIRC is max 5V, theoretically. I used them in this experimentation, localizing sound in space: http://sirloon.net/loonaweb/sirblog/localizing-sound-in-space-part-3-experimentation . They were interface with a PIC 16F88, ADC, Vref+ = 5V, Vref- = 0. Some optimizations probably can be done, but I've no idea what would be the optimial Vref+. That said, it worked nice with Vref+ = 5V.

Seb
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